In a conventional radio controlled toy, a carrier signal having frequency of around 27 MHz or around 40 MHz is generated by a transmitter. This carrier is modulated with a control pulse signal having frequency of around 50 Hz and the modulated carrier is transmitted to a receiver of a toy. The receiver demodulates the modulated carrier to produce a motor control pulse having the same frequency as that of the control signal and whose width may be larger than that of the control pulse signal. A motor of the toy is driven by the motor control pulse.
In detail, motor control for a toy such as an automobile includes a forward drive control, a backward drive control and a stop control. Therefore, the control pulse signal contains information concerning these controls. It has been usual that this information is contained in the control pulse signal as a difference in pulse width so that the receiver can detect either of them by comparing a trailing edge of the pulse with a trailing edge of a reference pulse which may be produced by any suitable means in synchronism with the control pulse signal. That is, the forward drive is detected when the trailing edge of the received control pulse signal is, for example, delayed from the trailing edge of the reference pulse; the backward drive can be detected when the trailing edge of the control pulse advances the trailing edge of the reference pulse and the stop instruction can be detected when the both trailing edges are coincident.
The steering control signal in the form of a pulse is also included in the control pulse signal. Therefore, the pulse width of the motor control signal and/or the steering control signal which is transmitted with an interval of about 20 msec. can not be made large enough to actually drive the D.C. motor which drives a movable member having a relatively large moment of inertia. Thus, the motor control pulse having a pulse width large enough to drive the motor is produced in the receiver side and corresponds to the motor control pulse signal and used to drive the motor.
On the other hand, in order to precisely drive the motor associated with the member having large moment of inertia, the pulse width of the motor control pulse should be made smaller. This means that the interval between a trailing edge of a pulse and a leading edge of a next pulse becomes large. Therefore, the motor can not keep its driven state by the former pulse until the next pulse due to the large momemt of inertia applied thereto.